PT - JOURNAL ARTICLE AU - David J. Nowak AU - Robert Hoehn AU - Daniel E. Crane TI - Oxygen Production by Urban Trees in the United States AID - 10.48044/jauf.2007.026 DP - 2007 May 01 TA - Arboriculture & Urban Forestry (AUF) PG - 220--226 VI - 33 IP - 3 4099 - http://auf.isa-arbor.com/content/33/3/220.short 4100 - http://auf.isa-arbor.com/content/33/3/220.full AB - Urban forests in the coterminous United States are estimated to produce ≈61 million metric tons (67 million tons) of oxygen annually, enough oxygen to offset the annual oxygen consumption of approximately two-thirds of the U.S. population. Although oxygen production is often cited as a significant benefit of trees, this benefit is relatively insignificant and of negligible value as a result of the large oxygen content of the atmosphere. Other benefits of the urban forest are more critical to environmental quality and human health than oxygen production by urban trees.